With development of modern society and people's awareness of environmental protection, more and more equipments use a rechargeable secondary battery as a power source, such as mobile phones, laptops, electrical tools, electrical automobiles and the like, which provides a broad space for application and development of the rechargeable secondary battery.
Generally, the electrical vehicles and energy storage stations need to use a high-capacity power battery as a power source. These power batteries should not only have high capacity, but should also have good safety and long cycle life, so as to reach the use standard and meet people's needs.
To ensure the safety of a power battery to a certain extent, generally a cap assembly of a power battery is provided with a vent. When the power battery has an accident caused by improper charging, short circuit, or exposure to a poor environment such as a high temperature environment, the power battery with high energy will produce a large amount of gas and temperature thereof will rise sharply, the gas bursts through the vent to release pressure, existence of the vent greatly improves safety performance of the power battery. The presence of the vent can improve the safety performance of the power battery to some extent, but if the energy gathered by the battery itself which is involved in the accident is not released, the power battery itself becomes a potential dangerous resource and there are still some safety problems left, if the power battery continues to be overcharged after involving the accident, more serious safety accidents will be caused.
A technical solution to solve the above problems is disclosed in the Chinese patent ZL201220419624.3, in which a resistance plate is additionally provided, and the resistance plate is provided in an insulating body, when an external short circuit of the battery occurs, a current of the external short circuit is controlled by the resistance plate, so as to protect the safety of a safety reverse valve and a short circuit protection conducting plate. For now, the structure in the above patent is complex, and the effect is not perfect when only the resistance plate is provided to control the current of the external short circuit.